High frequency circuit



P 1942- E. HEINECKE 2,297,410 I HIGH FREQUENCY CIRCUITS Filed Dec. 27,1939 /n ventor:

Eric/2 He/hedre Patented Sept. 29, 1942 i HIGH FREQUENCY CIRCUIT ErichHeinecke, Berlin, Germany; vested in the Alien Property CustodianApplication December 27, 1939, Serial No. 311,068 In Germany January 14,1939 2 Olaims.

This invention relates to high frequency circuits, especially of thekind intended for use in high frequency transmitters, and consists incertain features of novelty which will appear from the followingdescription and be pointed out in the appended claims, reference beinghad to the accompanying drawing, in which Fig. 1 is a diagramexplanatory of the art, while Fig. 2 shows a circuit arrangementaccording to my invention.

It is well-known to those skilled in the high frequency art that, inaddition to. the desirable fundamental frequency generated and/oramplified in the thermionic valves of high frequency transmitters,deleterious spurious oscillations of very high frequencies areoccasioned in such valves by several reasons. One cause for suchspurious oscillations resides in the fact that the. various electrodeleads located within the envelope of a thermionic valve constitute aconsiderable inductive impedance to oscillations of very high frequency.This condition particularly applies to the lead-in conductors for thecathode, as will be readily understood from the conventional circuitarrangement illustrated in Fig. l, in which the cathode lead-inconductor is represented by an inductive impedance I. It is evident thatthe anode circuit 2 and the grid circuit 3 are coupled with one anotherby this inductance which, under certain circumstances, may establishfeedback conditions in the overall circuit, with the result that theafore-mentioned spurious oscillations may be subject to self-excitationand in consequence thereof to considerable amplification.

It is the object of this invention to provide means in order to overcomethe disadvantages referred to in the foregoing. It is proposed accordingto the main feature of this invention to add supplemental elements tothe self-inductive cathode leads of a thermionic valve, which elementsare capable of translating the self-inductive effect of these leads intoa resistive eifect, thus offering a high ohmic component to undesirablespurious oscillations. The fulfillment of this condition would fullyexclude the above-mentioned self-excitation. Although a certain amountof coupling is present between the anode circuit 2 and the grid circuit3 in the arrangement of Fig. 1 in cases when the cathode lead Iconstitutes an ohmic impedance, as taught by this invention, thiscoupling does by no means give rise either to amplification or toself-excitation, since its effect is retroactive and therefore suitablefor fully suppressing existing spurious oscillations of highfreqeuncies.

The Fig. 2 is a wiring diagram illustrative to my invention. The cathodeK of a thermionic valve is provided with three lead-in conductors, eachforming an inductance, as indicated at Z1, Z2 and Z3. By interposing acondenser C1 and eventually a further condenser C2, these inductancesmay be tuned to the resonance frequency of spurious oscillations so thata pure ohmic resistance is rendered effective in the inner of the valvebetween the actual cathode 2 and the grounded point. Moreover, resistorsW1 and W2 may be shunted across these condensers so as to allow matchingof the artificially produced ohmic impedance to the specific operatingcharacteristics of the valve itself. This novel arrangement is not boundsolely to the resonance frequency, since the high degree of attenuationinvolved insures its effectiveness within a broader frequency band. Atfrequencies below the resonance frequency, the ohmic component as wellas the absolute value of the impedance between the cathode and thegrounding point is subject to a rapid decrease so that the effectivewave range remains unaffected.

For the sake of convenience, the capacities C1 and C2 may be formed bythe space capacitances existing within the tube between the separateelectrode leads or by the capacities between the connector elements ofthe valve socket. The magnitudes of these capacitances must be chosen soas to comply with the individual requirements.

This invention is by no means limited for use in connection with cathodeleads, since it is applicable to all kinds of electrodes which areequipped with more than one single lead-in conductor.

What is claimed is:

1. A circuit arrangement for high frequency transmitters for short andultra-short waves including an electron discharge device comprisingwithin an evacuatedcontainer a plurality of electrodes and a leadconnected to one of said electrodes having an inherent self-inductionwhich tends to set up spurious oscillations, characterized by theprovision of at least one additional lead connected directly to saidelectrode the space capacity between said first-mentioned lead and saidadditional lead being so dimensioned as to produce in combination withthe inherent selfinduction of the leads a resonant circuit tuned to thefrequency of said spurious oscillations, whereby the inherentself-induction effect is translated into a resistive effect of highohmic resistance for said spurious oscillations.

2. A circuit arrangement for high frequency transmitters for short andultra-short waves including an electron discharge device comprisingwithin an evacuated container a cathode and a lead connected directly tosaid cathode having an inherent self-induction which tends to set upspurious oscillations, characterized by the provision of at least oneadditional lead con- 0 nected to said cathode, the space capacitybetween said first-mentioned lead and said additional lead being sodimensioned as to produce in combination with the inherentself-induction of the leads a resonant circuit tuned to the frequency ofsaid spurious oscillations, whereby the inherent self-induction efiectis translated into a resistive efiect of high ohmic resistance for saidspurious oscillations.

ERICH HEINECKE.

